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Kansas soybean fields targeted

Aug 04, 2009

Grasshopper populations have continued to increase in central Kansas, particularly, and webworms have shown up in some southeast Kansas soybean fields, according to Kansas State University entomologist Jeff Whitworth.

"That´s a little surprising to find grasshoppers as young as we´ve seen recently, as their development is usually a little farther along by this time of year," said Whitworth, who is a row crop specialist with K-State Research and Extension. "However, as late as July 22 there were significant numbers of 1st and 2nd instar nymphs in pastures, grassy waterways and field borders."

Many different species are present, he said, but the two main species K-State scientists observed were the "slant-faced" `hoppers, which usually are not a problem for crops, and the two-striped or Packard grasshopper.

"Either the two-striped or the Packard species can be very destructive to pastures, waterways, and/or crops, so this is a great time to evaluate these areas for grasshoppers and apply controls if warranted," Whitworth said.

Reports of webworms in soybeans in southeast and central Kansas have also been coming in, he said.

"These worms may have two to three generations per year in Kansas and will get one inch long before they are mature enough to stop feeding and pupate," the entomologist said. "Remember, soybeans have an amazing capacity to compensate for early season defoliation, as they usually produce excess leaves anyway. Therefore, defoliation often looks worse than the actual impact later on yield. Soybean plants often compensate for stand losses with additional growth."